the fastest muscle car built was the 70 chevelle 454 LS6 450 HP. which was underated for insurance purposes and any car with the chrysler hemi 426, 425HP. underrated was a fast car if the 2 4bbls. were tuned right and had a set of headers on it. I have a 67 chevelle with a 454 LS6 that I installed and a 68 charger R/T 440.